Trying to get a copy of a Divorce Decree?

Hello, I’m Jason, and I have a question concerning a Divorce Decree. I have a niece that is trying to get a copy of her mother’s Divorce Decree, because she needs it to prove to Medicaid that her father on her Birth Certificate, is not her real father. My niece is 18 years old, and she is trying to get Medicaid to cover her medical expenses. And the only way Medicaid will approve her is that she gets that Divorce Decree. Her mom never raised her though, and she is having a very hard time getting it from her mom. Her mom had some prison time before, and is giving her daughter a hard time. So what should my 18 year old niece do to get her mom’s Divorce Decree without her? My niece is a very good girl, she is even going to college to be a nurse. My nieces mom got a Divorce in the state of Illinois, or Virginia, it is one of those states.